Piezoelectric and electrostrictive ceramic articles of lead zirconate titanate containing manganese and tungsten oxides



March 5, 1968 HlsAo BANNO 3,372,121

PIEZOELECTRIC AND ELECTROSTRICTIVE CERAMIC ARTICLES OF LEAD ZIRCONATETITANATE CONTAINING MANGANESE AND TUNGSTEN OXIDES Filed March 15, 1965 3Sheets-Sheet l increase il: reso/larice fregaenc F p I M I l0 T /00IUUOH 10000 une after/2o ar/za fm, aars H Sd o Ban no mwlm ATTORNEYSMal'dl 5, 1968 HisAo SANNO PIEZOELECTRC -AND ELECTROSTRICTIVE CERAMICARTICLES OF LEAD ZIRCONATE TITANATE CONTAINING MANGANESE AND TUNGSTENOXIDES 3 Sheets-Sheet 2 Filed March l5, 1965 with no addi@ `with add/ffmof WMM/03 ma 7m mfp/1,1 02

Z0 Tempemfu re @6) INVENTOR H is ao Ba r1 n 0 BY MM5 lf/777W, ATTORNEYSMarch 5, 1968 HlsAo BANNO 3,372,121

PIEZOELECTRIC AND ELECTROSTRICTIVE CERAMIC ARTICLES OF LEAD ZIRCONATETITANATE CONTAINING MANGANESE AND TUNGSTEN OXIDES ate of substfatianufff/1 rfar/tvm Z INV ENTOR Hlao Bann@ United States Patent OilcePatented Mar. 5, 1968 3,372,121 PIEZOELECTRIC AND ELECTROSTRICTIVECERAMIC ARTICLES F LEAD ZIRCON- A'IE TITANATE CGNTAINING MANGA- NESE ANDTUNGSTEN OXIDES Hisao Banno, Ueno-machi, Japan, assignor to NGK SparkPlug Co., Ltd., Nagoya, Japan Filed Mar. 15, 1965, Ser. No. 439,676 14Claims. (Cl. 252-623) ABSTRACT 0F THE DISCLOSURE Piezoelectric andelectrostrictive ceramic articles having a composition consistingessentially of Pb.(Zr-Ti)03 or PB (Zr-Sn-Ti)03 rwherein a part of Pb isreplaceable by at least one alkaline earth element selected from thegroup consisting of Ba, Ca, Sr and Mg, and containing W and Mn toparticularly improve mechanical Q of the ceramic articles which isespecially important in their application to a ceramic wave lter, amechanical wave filter and a piezoelectric tuning fork.

Itis well known that the ceramic material of solid solution of leadtitanate and lead zirconate, Pb(TiX-Zr1 x)03 shows the largestpiezoelectric and clectrostrictive effects when x=0.1 to 0.6 moreparticularly, at a composition of x=0.42 to 0.52 showing morphotropictransformation, and also the composition of Pb (TiZr-Sn)O3 consisting ofa solid solution of lead titanate, lead zirconate and lead stannatederived from the standard composition Pb(Ti-Zr) O3.

Moreover, it has also been known that the compositions expressed by(Pb-Sr) (Ti-Zr) O3 or (Pb-Sr) (Ti-ZrSn)O3 which is formed bysubstituting a part of Pb from the standard type of Pb(Ti-Zr) O3 and Pb(Ti-Zr Sn)03 derived therefrom, with one or more of alkaline earthmetals such as Sr, Ba and Ca at a rate less than 30 atom percent haveimproved electromechanical coupling coeliicient and dielectric constantif compared with the original type. I have already disclosed and claimedin my copending U.S. patent application Serial No. 289,81'1 filed onJune 24, 1963, that if 0.2-% by weight of tungsten oxide is added to theabove mentioned known compositions such as so-called PZT type ceramics,then electromechanical coupling coeiicient Kp, dielectric constant e andspecific electric resistance thereof are greatly improved and, inaddition, the time stability of the electromechanical coupling coecientand dielectric constant are QM, i.e., mechanical Q. Still another objectof the invention is to provide ceramic articles having excellentpiezoelectric and electrostrictive characteristics, especiallyepoch-making characteristics as elements of ceramic wave lters,mechanical Wave filters and piezoelectric tuning forks.

For a better understanding ofthe invention reference is taken to theaccompanying drawings showing characteristics of ceramic articles of theinvention when either one or both of tungsten oxide and manganese oxideare added to base -composition comprising lead-titanate-zirconatecompounds, in which FIG. 1 is a diagram illustrating time characteristicof electromechanical coupling coefcient Kp;

FIG. 2 is a diagram illustrating time characteristic of dielectricconstant e;

FIG. 3 is a diagram illustrating time characteristic of resonancefrequency Fr;

FIG. 4 is a diagram illustrating temperature charac- Following 4 sampleswereprepared starting from a common base composition of Pb(Zr051-Ti049)03 which was prepared by using PbO, TiO2 and ZrO2 -at a ratio of224.33 g. of PbO, 39.95 g. of TiO2 and 62.97 g. of ZrO2.

Sample A: with addition of both 2% rby Weight of W03 and 0.75% by weightof M1102 (composition of the present invention).

Sample B: with addition of 2% by Weight of W03.

Sample C: with addition of 0.75% by weight of MnO2.

Sample D: with no addition.

Each of the above samples was mixed, ground, molded, calcined at700-l000 C., ground again, shaped and then sintered Iat 1l00-1400 C. inPfbO atmosphere to obtain disks of about 0.8 mm. thick and about 20 mm.dia. The disks thus obtained were electroded and polarized tor 1 hourwith a direct current voltage of 40 kv./cm. at 80 C., lthen exposed tothe open air for a week and thereafter various characteristics weremeasured. The results also improved to a considerable extent. are shownin Table 1.

TABLE 1 Electro- Resistance Addition to a. base composition mechanicalat resonance Dielectric Mechanical Q, Sample Pb(Zr0 51-Ti0.4g)0zcoupling trequency R0 constant, e QM coetcient KD (ohm) (percent) A 2%by weight pltwWgg and 0.75% 60 2 1, 200 750 0 g. 2% by weight of W03...57 18 1, 500 85 by weight of MnO 30 15 700 500 one 42 15 800 300 Theprincipal object of the invention is to provide further improvement ofelectromechanical coupling coeiiicient Kp, dielectric constant e andspecic electric resistance as well as time and temperature stability ofPZT ceramic articles by simultaneously adding 0.2-20% by Weight oftungsten oxide and 0.075-7.5% by weight of manganese oxide to saidso-called PZT type ceramics as described in details hereinafter. Anotherobject of the invention is to provide ceramic articles having a veryhigh a dielectric constant e which is slightly lower than that of SampleB but highter than those of Samples C and D an electromechanicalcoupling coeflicient KIJ which is higher than any one of those ofSamples B, C and D an electrical resistance R at resonance frequency anda mechanical Q which are excellent and far exceed those of Samples B, Cand Dl The time stabilities of vthe electromechanical couplingcoefficient Kp, dielectric constant e and resonance frequency Fr areshown in FIGS. 1 to 3. It is apparent from FIGS. 1 to 3 that the ceramicarticles of the invention including 2% by weight of W03 and 0.75% byweight of MnOz have stable values of electromechanical couplingcoelcient Kp, dielectric constant e and resonance frequency Fr, 4andpractically no drift of any of the values was noticed throughout 4thetime of the measurement.

The temperature stability of the 'frequency constant Fr-D and thespecific electric resistance at elevated temperatures are improved to aconsiderable extent compared with those of samples having no additivesas shown in FIGS. 4 and 5.

Example 2 A part of -Pb in the base composition was substituted with Srto produce a new base composition consisting essentially of(PbU,95-Sr0,05)(Zr0,54-Ti0 46)03. Four different sample disks of about0.8 mm. thick and about 20 mm. dia. were prepared with said substitutedbase composition in Athe same manner as Example 1. The char- 4 weremeasured, and the results are shown in FIG. 6. It is apparent from FIG.6 that the additives are most elective when approximately 2% by Weightof W03 and approximately 0.75% by Weight of Mn02 are added.

Example 4 To a base composition @bha-Sra) (Zr0.52-Ti0.48)03 which was aderivative of Pb(Zr-Ti)O3 by partial substitution of Pb with Sr, 2% byweight of W03 and 0.75% by weight of MnO2 were added, and further 2% byweight of PbO was added to equilibrate with W03, that is to say theaddition rate of PbO was to be IPbOrWO3=l11 by mol orPbO:WO3=233.2:231.91:1 by Weight. The electromechanical couplingcoefficient Kp dielectric constant e and mechanical Q of samples thusprepared were measured, and the results are shown in FIG. 7.

It is apparent from FIG. 7 that the electromechanical coupling coeicientKp is gradually reduced as the rate of substitution with Sr for Pbincreases, and the dielectric constant e and mechanical Q give theirmaximum values at about 12.5 atom percent of rate of substitution withSr for Pb and at about 5 atom percent of the same rate respectively. Theeffects of adding W03 and MnO2 are apparent in FIG. 7.

acteristics of sample disks thus obtained were measured Example 5 andthe results are shown in Table 2. To the following compositions, whichwere typical com- TABLE 2 Electro- Resistance Addition to basecomposition mechanical at resonance Dielectric Mechanical Sample(Phan-Sms) (Zran-TiwO coupling frequency constant, e Q. QM

coencient Ro (ohm) Kp (percent) A' 2% by weight of W03 and 0.4% by 55 3700 1. 100

weight of MnOg. B 2% by weight of WO: 68 12 2, 000 70 C' 0.4% by weightof MnOg. 23 24 700 600 D None 48 10 850 300 It is apparent from Table 2that, except for the dielectric constant, the ceramic article of theinvention, which corresponds to the above composition A consistingessenltlally Of (Pb0 95*s1'0 05) (Zfg.54T0 46)O3 and addition of 2% byWeight of W03 and 0.4% by weight of MnO2, was provided with anelectromechanical coupling coeicient Kp which is lower than that ofSample B but higher than those of Samples C and D a resistance R0 atresonance frequency and a mechanical Q, which are especially excellenthaving a ratio of about 3.5 corresponding values of Sample D' which hasno additives Example 3 To a base composition of Pb(Zr0,51-Ti 49)03diierent amounts of W03 and MnOz were added while keeping the ratio ofthe two additives at WO3:MnO2=-4: 1.5 by weight. The electromechanicalcoupling coefficient Kp, dielectric positions produced by partiallysubstituting Pb of Pb(Zr-Ti)03 with Ba, Ca or Mg and a typicalcomposition consisting essentially of a solid solution oflead-titanate-zirconatestannate derived from the base composition of Theeffects of such additions on the electromechanical coupling coeicientKp, dielectric constant e and mechaniconstant e and mechanical Q ofsamples thus prepared cal Q were measured, and the results are shown 1nTable 3.

TABLE 3 Electromechanical Dielectrlc Mechanical Sample Compositioncoupling constant Q, QM

coeliclent e Kp (percent) E-l (Pbo .sn-Bae .175) (Zlo,s4-Tiu,4s) O s 561, 400 300 E-Z (Plinn-Baum)(Zl`o.s4-T1o.4u)0a+2 Wt. 52 1, 000 600percent WOM-0.75 wt. percent Mn02+2 wt. percent PbO F-l (Pham-08u .05)(Zru .54-Tlo,4a) Os 50 1, 000 250 F-Z (Phone-0910,05) (Zrn54-Tiu.4u)0s+2Wt. percent W03 48 750 550 +0.75 wt. percent MnOz-i-Z wt. percent PbOG-1 Pb (Zro,4sTi.41-SI1o.1o) 0a 44 900 200 G2 Pb(Zro,43Tiu,47-Sl'1n,1u)Ori-2 Wt. percent WGH-0.75 47 700 600 Wt. percentMn02+2 wt. percent PbO H-l (Pbo .ss-Mgons) (Zo .s2-Tin Je) O: 42 950 200H-2 (Phon-Mgmt) (Zro,m-Tin,4s)0s+2 wt. percent W03 50 I, 300 500 +0.75wt. percent MnOz-l-Z wt. percent PbO 1t is apparent from Table 3 thatthe addition of W03 and Mn03 to Samples E-l and F-l of which basecompositions are produced by partially substituting Pb with Ba and Carespectively, increases the mechanical Q to a great extent, almost twicecompared to those of compositions having no additives, despite the factthat the electromechanical coupling coeicient Kp and dielectric coustante thereof are slightly reduced by such additions.

Said addition to Sample G-1 of which base composition consistingessentially of a solid solution of lead-titanate-zirconate-stannate,increases the electromechanical coupling coeicient Kp slightly andraises the mechanical Q considerably up to three times as high as thatof composition having no additives, despite the fact that its dielectricconstant e is slightly reduced.

As clearly shown in the preceding descriptions, it was found that theaddition of tungsten and manganese, at a rate corresponding to 0.2-20%by weight of W03 and at a rate corresponding to 0.075-7.5% by weight ofMn03 respectively, to ceramic composition consisting essentially oflead-titanate-zirconate compounds or to ceramic composition consistingessentially of substitution products of lead in lead-titanate-zirconatecompounds with at least one alkaline earth element selected from a groupconsisting of Ba, Ca, Sr and Mg, improves various characteristics ofsaid ceramic articles required as piezoelectric and electrostrictivematerials, particularly improves mechanical Q of said ceramic articleswhich is especially important in their application to ceramic wavelilter, mechanical wave filter and piezoelectric tuning fork.

In addition to the above improvement in properties of ceramic articles,the addition of 2% by weight of W03 and 0.75 by weight of Mn03 reducesthe sintering ternperature of the ceramic articles from 1280-1300 C.which is necessary for sintering the composition of Pb(Zr-'I`i)03 havingno additives, to the level of 1200 C. Thus the above addition not onlyimproves the physical properties of the product, but also substantiallyfacilitates mass production of the ceramic articles.

According to the invention, tungsten and manganese can be added in theform of either metallic powder particles or compounds with otherelements, and their addition quantities should be within the range of0.2-20% by weight as yconverted to equivalent weight of W03 in case oftungsten and 0.075-7.5% by weight as converted to equivalent weight ofMn03 in case of manganese. The reason for setting the minimum limits at0.2% of W03 and at 0.075% of M1102 is due to the fact that the additionof said metals affects the physical properties of the ceramic articlesvery sensitively and an addition of 0.2% of W03 and 0.075% of M1102causes sufficient effects. The reason for setting the maximum limits at20% of W03 and at 7.5% of Mn02 is due to the fact that addition of saidmetals in excess of said maximum limits lresults in deterioration ofvarious physical properties of the productS.

In the base composition of Pb (Zr1 x-Tix)03, x is to be within the rangeof 0.1-0.6, because ceramic articles having compositions within saidrange give practicable values of electromechanical coupling coefficient.When the other base composition of Pb(Zry-SnZ-Tix)03, which is aderivative of Pb(Zr-Ti)03, x, y and z are to -be within the range ofx=0.1-0.6, y=0.9, and z=00.65 provided that x+y+z= 1, because said rangeof composition results in good over-all effects on various physicalproperties. The preferable ranges of the above x, y and z are :0.42-0.52, y=0-0.55 and z=00.58 provided that x+y+z=1, which are close to thecompositions showing morphotropic transformation.

When a part of Pb in the above base composition of Pb(Zr-Ti)03 orPb(Zr-Sn-Ti)03 is substituted with at least one alkaline earth elementselected from a group consisting of Ba, Ca, Sr and Mg, the rate of thesubstitution is to be less than 30 atom percent, because a substitutionin excess of 30 atom percent causes remarkable andlead-titanate-zirconate-stannate compounds expressed by the formulaPb(Zry-Sn3-Tix)03, wherein x=0.1 to 0.6, y=0 to 0.9, z=0 to 0.65provided that x+y-|-z=1.0, and containing tungsten at a ratecorresponding to 0.2 to 20% by weight of W03 and manganese at a ratecorresponding to 0.075 to 7.5% by weight of Mn02.

2. Ceramic articles according to claim 1, wherein a part of the lead insaid materials, which is less than 30 atom percent thereof, issubstituted with at least one alkaline earth element selected from thegroup consisting of barium, calcium, strontium and magnesium.

3. Ceramic articles consisting essentially of material selected from thegroup consisting of lead-titanate-zirconate compounds expressed by theformula and lead-titanate-zirconate-stannate compounds expressed by theformula Pb(Zry-SnZ-Tix)03, wherein x=0.42 to 0.52, y=0 to 0.55, z=0 to0.58 provided that and containing tungsten at a rate corresponding to0.4 to 5% by weight of W03 and manganese at a rate corresponding to 0.15to 2.0% by weight of Mn03.

4. Ceramic articles according to claim 3, wherein a part of the lead insaid material, which is less than 30 atom percent thereof, issubstituted with at least one alkaline earth element selected from thegroup consisting of barium, calcium, strontium and magnesium.

5. Ceramic articles according to claim 1, which contain a finitequantity of additional lead oxide not exceeding the stoichiometricproportion necessary to balance said tungsten oxide and manganesedioxide as PbO-W03 and Pb0-Mn03 respectively.

6. Ceramic articles according to claim 2, which contain a finitequantity of additional lead oxide not exceeding the stoichiometricproportion necessary to balance said tungsten oxide and manganesedioxide as PbO-WO3 and PbO-Mn03 respectively.

7. Ceramic articles according to claim l, which consist essentially oflead-titanate-zirconate compounds expressed by the formula Pb(Zr1X-Tix)03, wherein x=0.42 to 0.52 and contain about 2% by weight of W03and about 0.75% by weight of Mn02.

8. A ceramic article according to claim 1, which consists essentially ofPb(Zr0,51-'I`i3 43)03 and contains about 2% by weight of W03 and about0.75% by weight of M1102.

9. Ceramic articles according to claim 2, consisting essentially oflead-strontium-titanate-zirconate compounds expressed by the formula(Pb1, a-Sra) (Zr1 X-Tix)03, wherein a=0.02 to 0.15, 10:0.42 to 0.52, andcontaining about 2% by weight of W03 and about 0.4% by weight of M1102.

10. A ceramic article according to claim 2, consisting essentially of(Pb0,95-Sr0,05) (Zr0 54-Ti3,43)03, and containing about 2% by weight ofW03 and about 0.4% by Weight of Mn02.

11. Ceramic articles according to claim 2, consisting 7 essentially oflead-barium-titanate-zirconate compounds expressed by the formula (Pb1a-Baa) (Zr1 X-Tix)03, wherein a=0.02 to 0.20, x=0.42 to 0.52, andcontaining about 2% by Weight of W03 and about 0.75% by weight Of M1102.

12. A ceramic article according to claim 2, consisting essentially Of(Pb0-825-Ba0 175)(ZO.54TO.4G)O3, and COD' taining about 2% by Weight ofW03 and about 0.75% by weight of Mn02.

13. A transducer element comprising a piezoelectric and electrostrictiveceramic article according to claim 1.

14. A transducer element comprising a piezoelectric and electrostrictiveceramic article according to claim 2.

References Cited UNITED STATES PATENTS 4/1961 Plessner et al. 106-398/1966 Kulesar 252-629 OTHER REFERENCES Matsuo et al., Lead TitanateCeramics Doped with Manganese Oxide, Journal of the American CeramicSociety, vol. 48, No. 2, February 1965.

TOBIAS E. LEVOW, Primary Examiner.

ROBERT D. EDMONDS, Examiner.

